DESCRIPTION Breast cancer is the most common cancer in women with early 200,000 new cases diagnosed each year in the United States. The America Cancer Society reports 43,000 women die each year from breast cancer. Current screening methods include physical examination and mammography. Mammograms are very sensitive and can detect non-invasive or small (<1 cm in diameter) invasive cancers that have the best prognosis. Though mammograms and routine breast exams have greatly improved early detection and thus early treatment of breast cancer, they fall short of an ideal screen. Both detect abnormalities which usually are benign. Indeed, about 5% of mammograms are rated as "suspicious" or "probably malignant", and of these, approximately 80% are subsequently found; through biopsy, to reflect benign masses. It is extremely expensive to eliminate false positives and the detrimental psychosocial consequences of false positives greatly impact women's lives. Clearly, a more specific test is needed to discriminate between benign and malignant breast disease.